Platemaking method for lithographic printing plate precursor and planographic printing method

Abstract

A platemaking method for a lithographic printing plate, comprises: imagewise exposing a lithographic printing plate precursor comprising: a hydrophilic substrate; and a negative image recording layer containing a water-insoluble polymer; and removing a non-exposed area of the image recording layer with an aqueous solution, wherein a temperature of the aqueous solution is higher than a glass transition temperature (Tg) of the water-insoluble polymer.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This is a Divisional of co-pending application Ser. No. 11 / 139,775 filed in the U.S. on May 31, 2005, which claims priority on Japanese Applications No. 2004-161252 filed on May 31, 2004, No. 2004-188420 filed on Jun. 25, 2004, No. 2004-230949 filed on Aug. 6, 2004, and No. 2004-235842 filed on Aug. 13, 2004, the entire contents of which are hereby incorporated by reference and for which priority is claimed under 35 U.S.C. § 120.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to a platemaking method for a lithographic printing plate and a planographic printing method, and more particularly to a platemaking method for a negative lithographic printing plate in which an unexposed portion of an image recording layer is removed with an aqueous solution and a planographic printing method improved in an on-press developability and an inking property.[0004]2. Description of the Related Art[0005]In gen...

AI Technical Summary

Benefits of technology

[0033]The function mechanism of the invention is not necessarily made clear, but it is estimated, in the platemaking method, that the water-insoluble polymer in an unexposed portion of the image recording layer is softened by heating to a temperature higher than Tg in the solution, thereby facilitating a penetration of water into the image recording layer and improving the developability significantly. Also in the planographic printing method of the invention, the lithographic printing plate precursor is contacted, after the imagewise exposure, with an aqueous solution containing a hydrophobic organic compound and a water-soluble polymer compound whereby it is estimated that the hydrophobic organic compound is adsorbed on the image area, cured by the exposure, to form an oleophilic surface thereby improving the inking property and the hydrophobic organic compound together with the hydrophilic component penetrates into the unexposed and uncured image recording layer thereby improving the developing property.

Problems solved by technology

However, such technologies are still insufficient in a developability or in a printing run length.

However, such method of forming an image by mere thermal fusion of fine particles, though showing a satisfactory on-press developability, shows an extremely weak image strength (adhesion to the substrate) and has an insufficient printing run length.

However, the on-press developable lithographic printing plate precursor utilizing such polymerization reaction can provide an improvement in the run length, but is insufficient in the practical on-press developability.

Also for enabling an on-press development, the on-press developable lithographic printing plate precursor has to contain a considerable amount of a hydrophilic component in the image recording layer, and is therefore inferior in an inking property.

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